1. Technical Field
This invention relates to high precision manufacturing tools in general, and in particular for example, to motor driven leveling stages that are capable of adjusting the angular position of a work piece relative to a reference plane or surface with micro-arc-second precision.
2. Related Art
Many manufacturing processes entail the positioning of a work piece at a precise angle relative to a reference plane defined by, e.g., a surface plate or a cutting tool. For example, in the fabrication of certain types of semiconductor packages, it is necessary to machine semiconductor wafers or to electrically interconnect a semiconductor die with another die or an interconnective substrate, e.g., by means of cold-fused bumps of solder or a conductive adhesive. To effect these processes reliably, it is necessary to align the components precisely relative to the cutting tool or each other before the cuts or interconnects are made.
In the conventional machining of parts, skilled machinists sometimes use an apparatus referred to as a “sine bar” or “sine plate” to position a work piece at a selected angle on a bed or work surface of, e.g., a milling or grinding machine, and relative to a cutting or grinding head so as to produce a milled surface on the work piece that is disposed at a precise angle relative to the work surface. With reference to FIG. 15, a conventional sine plate 10 comprises a pair of flat lower and upper plates 12 and 14 that are hinged to each other at one end by a hinge or pivoting mechanism, such as a first cylindrical roller 16, so as to enable the opposite ends of the two plates 12 and 14 to open and close relative to each other like a clam shell. A second roller 18 may be disposed between the two ends of the plates opposite the first roller at a distance Y therefrom. The lower plate 12 is disposed on a reference surface, e.g., the upper surface of a surface plate 20 or the bed of a milling or grinding machine, and a work piece 22, shown by a dashed line outline in FIG. 15, is disposed on the upper plate 14. The size of the angle θ subtended between the upper and lower plates 12 and 14 is adjusted by inserting one or more shims or gage blocks 24 having a total thickness of X between second roller 18 and the upper surface of the lower plate 12, and is given by θ=sin−1 X/Y.
Although the conventional sine plate 10 of FIG. 15 is capable of being used to adjust the angle of a work piece 22 relative to surface plate 20 with some accuracy, it requires some manual skills on the part of the worker, is relatively cumbersome and time-consuming to set up and use, and is incapable of micro-arc-second precision. Additionally, because the apparatus lacks a protective enclosure, its use in an environment in which caustic fluids or vapors are present, such as in a semiconductor fabrication facility, is contraindicated.
Accordingly, a need exists for a motorized leveling stage that is protected from any hazardous elements in the work environment, such as caustic fluids, and that can be set up easily and then controlled from a remote location to adjust the angle of a work piece relative to a reference plane with micro arc-second precision.